158 CLASS MAMMALIA. 



the fur on the upper part of the body is of a pale fawn- 

 colour, mingled with gray, and underneath of a beautiful 

 white ; the tail, shorter than that of the Tamaricin, is the 

 same colour as the back, and has neither rings nor spots ; 

 a longitudinal line of a reddish-brown is observable under 

 the centre of the belly. 



This animal inhabits the sandy and burning deserts 

 which border on the Caspian, and which are situate be- 

 tween the Volga and the Ural. It digs burrows, and lives 

 on the nuts of the Pterococcus Aphyllus, 8fc. 



The next species we shall notice is the Gerbillus JEgyplius, 

 sometimes called the Long-legged Rat, and is the same as 

 the Dipus Pyramidum of M. Geoffroy. 



This species must not be confounded with the Gerbillus 

 of the torrid zone. There is a notable dissimilarity in the 

 proportions of the hinder extremities, they being much more 

 slender and elongated in this than in the other species. 

 There is also a difference of size between these Rodentia, 

 for the Egyptian Gerbillus is hardly as large as a Mouse, 

 while the other may be considered as intermediate between 

 the Mulot and common Rat. 



An individual described by M. Olivier had a conical and 

 pointed head, like the Rats; ears oval and moderate ; mus- 

 tachios long ; and very short neck ; the fore-paws were very 

 short, provided with five toes, the four exterior toes being 

 armed with crooked claws; the internal, or thumb, was very 

 short, and without nail ; the hinder feet were as long as 

 the body, very strong, almost naked, and provided with six 

 unguiculated toes, almost equal in length ; the tail was a 

 little longer than the body, covered above with small brown 

 hairs, and terminated by hairs more elongated ; all the 

 upper part of the body was of a clear yellow, and the under 

 part of a pure white. 



This animal was met near Memphis, coming out of the 

 burrow which he inhabited. 



